Thorold Tunnel opening ceremony photographs, September 18,1968.

Construction on the Thorold tunnel began in 1965 and was completed in 1967. It was designed by H. G. Acres & Company Ltd. and built by Pitts-Atlas, a joint venture of C.A. Pitts, General Contractor Ltd., and Atlas Construction Company Ltd. The tunnel replaced two lift bridges (Bridge 9 at Ontario Paper Co. and Bridge 7) that carried traffic over the Welland Canal. The majority of the construction occurred during the winter months, when the canal was closed to shipping. The water was drained and concrete sections shaped liked tubes were poured, creating the tunnel. During the summer months, the end sections of the tunnel were constructed so that shipping could continue uninterrupted. The 24 million dollar project was financed jointly by the Department of Highways and the St. Lawrence Seaway Authority. The tunnel was officially opened on September 18, 1968.